Construction and agricultural vehicles such as tractors are usually provided with a step-down geared auxiliary transmission known as a power take-off. The power take-off is directly connected to the vehicle engine and has an output shaft or power take-off shaft connectable to ancillary construction and farming devices such as cranes and harvesting equipment. A coupling between the engine and the power take-off shaft is actuatable independently of the vehicle drive. Frequently the power take-off coupling includes a wet-type disk clutch which in a disengaged or uncoupled state exerts a drag force on the power train driving the output shaft, whereby the same continues to rotate. This rotation is a potential cause of accidents.
One attempt to remove this source of accidents, described in German patent document (Auslegeschrift) DT-AS No. 2,522,411 (see U.S. Pat. No. 4,108,291), involves the application of a braking force to a nonsliding cylinder member of the power take-off coupling upon disengagement thereof. A brake shoe pushes against the cylinder under the action of a spring and is retracted or shifted away from the cylinder by pressurized fluid actuating the coupling. Upon disengagement of the coupling via depressurization of the fluid, the brake is forced against the coupling cylinder by the compressed spring to arrest motion of the output shaft. This shaft remains locked even upon shut-off of the vehicle engine and is, therefore, at no time capable of being manually turned.